Sulfur-containing polyamine curing agents for polyurethanes and method for making and using the same

ABSTRACT

Sulfur-containing polyamine curing and hardening agents for polyurethane prepolymers and methods for preparing them from thiol-containing aromatic amines and from benzothiazoles. Some of the new compounds are liquid at ambient or mixing temperatures. These are particularly advantageous because they are more uniformly mixed with polyurethane prepolymers, and therefore yield elastomers of improved physical properties at low curing temperatures.

United States Patent Hirosawa et al.

[4 1 Nov. 18, 1975 SULFUR-CONTAINING POLYAMINE CURING AGENTS FOR POLYURETHANES AND METHOD FOR MAKING AND USING THE SAME Inventors: Frank N. I-Iirosawa, Monterey Park;

Ming Hsing Lee, Glendale, both of Calif.

Assignee: Furane Plastics, Inc., Los Angeles,

Calif.

Filed: Oct. 26, 1973 Appl. No.: 410,233

Related US. Application Data Division of Ser. No. 60,742, Aug. 3, 1970,

abandoned.

us. c1..... 260/775 AM; 260/578; 260/75 NM Int. Cl. C08G 18/38 FieldolSearch...260/77.5 AM,2.5 AM,75 NM [56] References Cited UNITED STATES PATENTS 2,765,341 10/1956 Wirth et a]. 260/775 AM Primary Examiner-M. J. Welsh Attorney, Agent, or Firml(enneth G. Wheeless; Robert P. Auber ABSTRACT uniformly mixed with polyurethane prepolymers, and

therefore yield elastomers of improved physical properties at low curing temperatures.

12 Claims, No Drawings SULFUR-CONTAINING POLYAMINE CURING AGENTS FOR POLYURETHANES AND METHOD FOR MAKING AND USING THE SAME This application is a divisional application of Ser. No. 60,742, filed Aug. 3, 1970 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a new group of sulfur-containing polyamine hardeners in liquid and solid form for use in the production of cured urethane resins, and to processes for their preparation and use.

By the use of these new hardeners for curing diisocyanate compositions, elastomers are formed having improved handling characteristics and improved physical properties.

Polyurethane polymers are formed by reacting a dior poly-functional isocyanate with polyether polyole or with hydroxyterminated polyesters. In reacting monoisocyanate with a compound containing a simple reactive hydrogen, a single urethane is formed. If the two reactants are bifunctional, the resulting product is polymeric; and if one of the reactants is polymeric, the ultimate product will be a polymer of high molecular weight. Such a compound with reactive isocyanate terminated polymers that may be further chain extended, cross-linked, cured, or hardened to high molecular weight compound is represented, typically, in the following equation:

The prepolymer which contains an excess of unreacted isocyanate groups may be subsequently chain extended, cross-linked or cured by reacting with polyamine compounds, producing linkage of the substituted area type as, for example, in the following equation:

H(1H HT) OH where R and R represents an alkyl, cycloalkyl, aryl, arakyl or alkene hydrocarbon.

The reaction of the type shown above has been employed in the preparation of the polyisocyanate prepolymers which have viscosities ranging from several hundred centipoises to solid plastic material.

It is generally recognized that aromatic amine cured elastomers will have higher modulus increased tensile strength, better tear strength, greater solvent resistance, and usually require much shorter cure time than glycol cured elastomers.

In spite of the superiority of the commonly used arylene diamine compounds (e.g., 4,4'-methylene bis (2- chloroaniline), and 3,3 -dichlorobenzidine) as curing agents for urethane resins, wherein good physical properties of the final polymers are attained, the use of these materials is attended with certain disadvantages that have limited more widespread acceptance. Specifically, these substances have relatively high melting points, making it difficult to get uniform mixes. The initial mixing is sometimes effected by powdering the curing agent, but even then, due to the elevated melting point, the material must be melted and uniformly dispersed in the polyisocyanate prepolymer which it is intended to cure. This heating to attain melting shortens the working life considerably, and at times, the mixture sets to an insoluble, infusible polymer before it can be mixed properly.

SUMMARY OF THE INVENTION The reaction of isocyanate with compounds that contain a nitrogen-hydrogen bond has been found to be governed primarily by the basicity or nucleophilicity of the nitrogen-hydrogen bond. The basicity of aromatic amine is decreased when electronegative groups, such as sulfur, halogen atoms or nitro groups are introduced in the nucleus, and especially the ortho-situated groups exert the greatest effect. We have discovered that sulfur is particularly advantageous in this respect. By condensing thiol-containing aromatic amines with an organic compound containing reactive halogen atoms (or other suitable reactive substituents) which are split off by reaction with an alkali metal hydroxide or an alkaline earth metal hydroxide, we have produced the new sulfur-containing polyamine hardeners for polyurethane prepolymers.

One object of this invention is to provide a new type of curing agent containing sulfur for curing polyisocyanate prepolymers. Another object is to provide a curing agent in liquid from for easy uniform mixing with the polyisocyanate prepolymers, which results in optimum properties when cured at the ambient room temperature. A further object is to provide a liquid curing composition that can be used as a hardener, crosslinking agent, or chain extender for polyisocyanate preopolymer compositions so as to produce elastomers having improved handling characteristics and improved physical properties.

Still another object is to provide a liquid curing agent that can be compounded with conventional compounding ingredients such as carbon black, silica, or coloring ingredients, and be subsequently mixed with polyisocyanate prepolymers to form highly useful polyurethane elastomers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS S-R-S@ R" 3 4 where R is an alkyl, cycloalkyl, aryl, arakyl, or alkene bis-(2-chloi'oethoxy)ethane; dichloro ethyl formal; dihydrocarbon, or an ester, or a urethane group; and R chloromethyl diphenyl oxide; 1,2,3-trichloropropane;

may be H, F, Cl, Br, I or a suitable substituent selected 1,1,3-trichloropropane; dihydroxy ester of chlorofrom the following: (1) alkyl groups of l to 18 carbon acetic acid [ClCl-l COOROOCCl-l Cl] with e.g., ethylatoms in any of their isomeric forms and substituted on 5 ene glycol, castor oil, propylene glycol, polyethylene the benzene nucleus in the ortho, meta, or para posiglycol, polytetramethylene ether glycol, etc.; dicarboxtions; (2) alicyclic groups of 3 to 18 carbon atoms such ylic acid ester of ethylene chlorohydrin 36 as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, CICH CH OOCRCOOCH CH Cl] with e.g. adipic methylcyclohexyl, etc.', (3) aromatic or arakyl groups acid, azelaic acid, dimer acid, etc.; urethane adduct of of the 6 to 18 carbon atoms such as benzyl, cumyl, etc. 10 ethylene chlorohydrin This compound may be produced by prereacting a mixture of aminobenzenethiel, alkali metal hydroxide or [CICH2CHZOOCNHRNHCOOCHZCH2CI] alkaline-earth metal hydroxide, and an active polywith e.g. 2,4-tolylene diisocyanate, 30/20 mixture of halogen compound. 2,4 and 2,6-tolylene diisocyanate, 4,4-methylene bis The reaction is illustrated in the case of ethylene di- (phenyl isocyanate) etc.; polyurethane adduct of ethylchloride as follows: ene chlorohydrin IY H7. m N L 2 @sn 2NaOH+C1 c11 c1-1 c1- (Em-on on. 2 NaCl where -Sl-l may be on the ortho, meta, or para posi- [CICH2CH2OOCNHRNHCOOR'COONHRNH tion on the benzene nucleus. GCH CH Cl] We have also found that the final product of the present invention may be obtained effectively by simultaneous alkali metal or alkaline earth metal hydroxide dichloropolyethylene Oxide hydrolysis and dehydrohalogenation with accompany- 2 2 )n z 2 dichloropolypropylene ing condension of benzothiazole and active halogen or- Oxide [CICH 3) 2 2 ganic compounds as illustrated in the following equa- 3) )n 2 3) dichloropolytetramethylene tion: 3 ether [Cl(CH CH CH CH O) CH CH CH CH Cl].

S I R 4 H (aqueous solution) reflux s-n -s MA 7 2 iCl-R -Ct a-Q I DR ZNaCI ZHCOCNa where R is an alkyl, cycloalkyl, aryl, arakyl or alkylene Although the examples given above have been dihydrocarbon, or an ester, or'a urethane 'group; and R 40 rected to the use of chlorine compounds, it is obvious may be H, F, Cl, Br, I, or a suitable substituent selected that the other halogen compounds such as bromine, iofrom the following: (1) alkyl groups of l to 18 carbon dine, or fluorine, are equally applicable in this invenatoms in any of their isomeric forms and substituted on tion.

the benzene nucleus in the ortho, meta, or para posi- For the preparation of the novel hardener composition: (2) alicyclic groups of 3 to 18 carbon atoms such tion, the appropriate amount of an aminobenzenethiol as cyclopropyl, cyclobutyl, cyclohexyl, methylcywas placed in a reaction vessel and an appropriate clohexyl, etc.: (3) aromatic or arakyl groups of 6 to 18 amount of aqueous solution of alkali metal or alkalinecarbon atorris such as benzyl, cumyl, etc. earth metal hydroxide was slowly added over a period Representative examples of the thiol-containing aroranging from 0.5 to 2 hours. After the completion of matic amines and thiazole derivatives useful in this inthe first stage of the reaction, an appropriate amount of vention are reactive poly halogen compoundwas slowly added over 2-aminobenzene thiol, a period ranging from 0.5 to 4 hours. After the comple- 4-aminobenzene thiol, tion of the second stage of the reaction, the mass was Benzothiazole, refluxed over a period of l to 24 hours to complete the Naptho 1,2] thiazole, reaction, and the hardener purified in the usual manner Naptho [2,1] thiazo1e which includes removing the salt water by washing, and Among the active poly halogen compounds which stripping of water and unreacted materials under remay be employed in the present invention are: methyduced P lene dichloride; l,l-dichloroethane; l,2-dichloroe- In another -PP forthe p p 0f the novel thane; l,2- dichloropropane; 1,3-dichloropropane; 2,3- hardfmer composmonsz the 'PP QI amount of dichloro-l-propene; 1,2-(or 1,3-; 2,3-) dichlorobutane; zothlqzole was P a a e q Vessel, alfld an P- propriate amount of aqueous solution of alkali metal or "l-d'h' -2-bt 1,4- fig ggi gg z i ik or g $52 Ti alkaline-earth metal hydroxide was added, and refluxed ene; 1,3 dichloro z methyl 2 pheny]pmpane; 12 (Or for a period ranging from 1 to 10 hours. After the coml,3; l,4-)-bis(chloromethyl) benzene; 1,3-bis- 5 pletion of the hydrolysis reaction, an appropriate (chloromethyl) 4,6 dimethylbenzene; bis( amount of reactive poly-halogen compound was slowly chloromethyl) ether; bis-(2-chloroethyl) ether; bis-(2- added f. a Period ranging froth 4 hours and the refluxing continued for a period ranging from 1 to v chlorolsopropyl) ether bis (4 chlorobutyl) ether 24 hours to complete the reaction. The hardener was purified in the usual manner which includes removing the salt water by washing, and stripping off water and unreacted materials under reduced pressure. The product obtained was usually of such purity it needed no further purification prior to use for its intended purpose.

The cured polyurethane polymers of this invention have many applications. They are particularly useful for potting and encapsulation of electrical equipment, for solid tires, for mechanical goods, such as sealing rings, packing gaskets, mountings, matting, printing ink rollers, etc.

The preparation of the novel sulfur-containing polyamine and the use of such curing agents will be further illustrated by the following specific examples, but it will be understood that the invention is not limited thereto. The reactants, their proportions and the specific ingredients of the formulations are presented as being typical, and various modifications may be made in view of the foregoing disclosure. Unless otherwise specified,

parts and percentages are by weight.

EXAMPLE 1 A 500 ml., 3 neck reaction flask, equipped with a mechanical stirrer and reflux condenser was charged with 125 grams (1 mole) of 2-aminobenzenethiol (2-ABT). With good agitation and cooling, a solution of 40 grams (1 mole) of sodium hydroxide in 60 grams of water was slowly added over a period ranging from 5 to minutes. The addition was controlled so that the reaction temperature did not rise over 95-l00C. To the above sodium-2-aminobenzenethiol (Na-Z-ABT) solution, 50 grams (0.506 mole) of ethylene dichloride was added over a period of 3 hours at pot temperature of 90-95C. After the addition, the mixture was reacted at l00105C. for an additional 4 hours. Water (200 ml.) was then added and stirred for a few minutes and phase separated. The aqueous salt solution was discarded and the organic layer was washed 2 times with 100 ml. portion of water and distilled under reduced pressure of mm. to pot temperature of 130C. The distillation residue was filtered while hot to remove the residual salt. The filtrate, weighing 274.7 grams (99% of the theoretical yield), a yellowish white solid, recrystallized 3 times from methanol, a white solid had a melting point of 75.576.5C.

Analysis Calcd. for C H N S C% H% N% S(by difference) Calcd. 60.86 5.79 10.10 23.21 Found 60.62 5.82 9.99 23.57

EXAMPLE 2 6 to reflux temperature (971l3C.) for 2 hours. Organic layer was then separated while hot and washed 3 times with 250 m1. portion of boiling water. The oily crude product thus obtained weighed 135 grams (98% yield), crystallized into a yellowish white solid with melting point of 7274C.

EXAMPLE 3 A 500 ml., 3 neck reaction flask, equipped with a mechanical stirrer, thermometer, and reflux condenser was charged with 125 grams (1 mole) of 2-ABT. With good stirring and cooling, a solution of 40 grams (1 mole) of sodium hydroxide in 60 grams of water was slowly added over a period of 5 to 10 minutes. The addition was controlled so that the final addition temperature remained below 100C. To the above Na-2-ABT solution, 43 grams (0.506 mole) of methylene chloride was added over a period of 3 hours at pot temperature of 75C. After the addition, the mixture was reacted at l00105C. for 4 hours. ml. of water was then added and stirred for a few minutes at 6080C. and phase separated. The aqueous salt solution was discarded and the organic layer washed twice with 100 ml. portion of water and distilled under reduced pressure of 25 mm. to pot temperature of C. The distillation residue was filtered while hot to remove the residual salt. The low viscosity, dark tan colored filtrate weighed 112 gm. (85.5% yield).

EXAMPLE 4 Five moles of Na-2-ABT solution as prepared in EX- AMPLE 1, 300 grams (2.65 moles) of 1,2-dich1oropropane was reacted at 6589C. for 30 minutes and the mixture was refluxed 20 hours at temperature of 93108C. The reaction mixture was purified as in EX- AMPLE 1 to obtain 652 grams (90% yield) of brown liquid of the following physical properties: Brookfield viscosity, 1,510 cps (25C.); n 1.6621; D 1.195; Amine eq. wt. (theo. 145).

Analysis Calcd. for C l-l N S C% H% N% S (by difference) Calcd. 62.06 6.20 9.65 22.09 Found 62.10 6.08 9.42 22.40

EXAMPLE 5 EXAMPLE 6 The curing agent prepared as in EXAMPLES l to 5 above may be mixed with a polyisocyanate prepolymer and the mass cured at room temperature or slightly above room temperature to provide a resilient, tough, rubber-like elastomer.

The liquid polyisocyanate prepolymer used as described above with the new curing agent consisted of Twenty-three parts of this hardener mixed thoroughly with 100 parts of polyisocyanate prepolymer- (amine eq. wt. 650), gave a polyurethane elastomer of excellent physical properties.

the reaction product of'(l) polytetramethylene ether glycol (PTMEG, manufactured by Quaker Oats Co.), and (2) an 80/20 mixture of 2,4- and 2,6-tolylene diiso- EXAMPLE 9 y the p i p to two moles y Weight Following the procedure described in EXAMPLE 1, e Polymene P X Whleh y be e to P p substituting bis( 2-chloroethyl)ether for ethylene dih lsocyanate'temlmated p p y melllde the chloride, gave an 80.5% theoretical yield of low viscos- P y y ether y e polyalkylenearylehe ity brown liquid. Twenty-three parts of this hardener ether glycols', the hydroxy terminated polyesters, such were mixed thoroughly with 100 parts of polyisocyaas P y y adlpate, P y y aebaeete, and nate prepolymer (amine eq. wt. 650), yielding a poly.- the The Polyol e) e represented y the formula: urethane elastomer of excellent physical properties. HO( RO),,H where R 1s e1ther an alkylene radical containing up to 10 carbon atoms, or alkylene-arylene ester group containingmolecule and n is an integer suf- EXAMPLE l0 ficiently large so that the molecular weight of the poly- Following the procedure described in EXAMPLE 1 meme polyol.ls 400 to 9 1,2,3-trichloropropane (75 grams, 0.508 mole) was Any of a'wlde vanety of orgalnc dusocyanate may be added into a solution of Na-Z-ABT 1.5 moles) over a employed to prepare? the polylsocyanate grepolymer' period of 1.5 hours at a pot temperature of 80-85C. f g gi mcludei g dllsoganate The mixture was further reacted at 100 1 10C. for 16 gp fi z z g i i eny 5 usocyaj hours. 187 grams (90.5% yield) of low viscosity brown na y eny ene usocyimate 25 liquid was obtained after the purification. This hardmethyle.ne blswbenyl lsocyailate) and the Y ener when cured with polyisocyanate prepolymer (eq. Comparatlve physical propertles of the urethane wt 658) had a Shore A hardness and had a elastomers cured w1th these hardeners and MOCA I workmg life of approximately 30 minutes at ambient (4,4 -methylene b1s( 2-chloroan1l1ne are listed 1n Table I room temperature.

TABLE I Polyisocyanate Eq. Curing Amount PBW Working Hardness Tensile Elongation Tear Prepolymer Wt. Agent 100 PBW Life Shore A Strength Strength 8158-A 675 I MOCA 19.8. 10 min. at 65C. 94 4830 390 650 8158-A 675 Exp. 4&5 21.5 min. at C. 75 7630 570 380 8666-A 375 Exp. 4&5 38.6 60 min. at 25C. 75 (D) 4350 230 930 5741-A 658 '22 25 min. at 25C. 83 4435 340 490 5712-A 675 21.6 20 min. at 25C. 3640 570 190 5721-A 1 1300 11.6 20 min. at 25C. 4270 570 1 180 8l58-A 675 Exp. 1&2 20.5 25 min. at 25C. 75 Comparable with Example 2 8l58-A 675 Exp. 3 19.4 min. at 25C. 85

EXAMPLE 7 EXAMPLE ll Following the procedure described in EXAMPLE 1, Following the procedure described in EXAMPLE 1,

substituting l,4-dichlorobutane (64.5 grams, 0.507 mole) for ethylene dichloride, a product of a light brown low viscosity liquid was obtained with a theoretical yield of better than 95%. This hardener, when cured with an equivalent weight of polyisocyanate prepolymer having an amine equivalent weight of 650, gave a Shore A hardness of 73, andhad a working life of better than 20 minutes. i

. EXAMPLE 8 Following the procedure described in EXAMPLE 1, substituting 1,4-dichlorobutene-2 for ethylene dichloride, yielded a product with m.p. 6468C. (theoretical yield of 98.5%).

Analysis Calculated for C H z z 1 C% 'H% N% i S (by difference) Calculated 63.57 5.98 39.24 21.21 Found 65.4] 6.06 8.76 19.77

substituting 140 grams (0.502 mole) of chloromethylated diphenyloxido (Dow Chemicals CMDPO-25) for ethylene dichloride, yielded 215.5 grams (97% yield) of soft yellow solid composition. This also gave a hard urethane elastomer of excellent physical properties.

EXAMPLE 12 An adduct of the following structure was prepared:

by addition of distilled ethylene chlorohydrin (67 grams, 0.83 mole) to distilled 2,4-tolylene diisocyanate (69 grams, 0.39 mole) and the mixture was reacted at -90C. for 1.5 hours. The crude product yield) was recrystallized once from benzene to give a crystal with m.'p. of 9395 C.

The adduct prepared as above (50.3 grams, 0. 15 mole) was reacted with 0.316 mole of Na-Z-ABT solution at a temperature of l l0l 14C. for 3 hours to give 74.5 grams (97% yield) of viscous hardener. The amine equivalent weight was 268 (theo. 256). Twenty-seven EXAMPLE 1 3 An adduct of the following structure was prepared:

l CICHZ -ca -O-C-N by reacting polyisocyanate prepolymer 130 grams, 0.2 mole) and 19 grams (0.223 eq.=) of ethylene chlorohydrin at 8590 C. for 4 hours. A solution of Na-2-ABT (0.106 mole) was mixed with a solution of above adduct (73 grams, 0.05 mole) in 50 ml. of toluene and refluxed for 3 hours at 9498C. The product thus obtained was a light brown, viscous, resinous composition weighing 75.5 grams (92.5%yield), and had an amine equivalent weight of 1015. This hardener when cured with an equivalent weight of polyisocyanate prepolymer (amine eq. wt. 650), gave Shore A hardness of 55, and had a working life of better than 1 hour.

EXAMPLE 14 (4,4'-methylene bis(2-chloroaniline), which had a working life of minutes at 65C. Both products showed comparable tensile strength but with the curing agent of above Example 14 had an elongation of 560% compared to the MOCA cure of 350%.

EXAMPLE 15 Following the procedure described in EXAMPLE 2,

substituting 1,4-dichlorobutane (64.5 grams, 0.507

mole) for ethylene dichloride, yielded a product of brown, low viscosity liquid, which when reacted with the prepolymer, gave a polyurethane elastomer having physical properties comparable to samples cured as described in Example 7.

Although the discussion and the examples have been directed to the hydrolysis treatment of benzothiazoles and of the 2-aminobenzenethiol in the form of its sodium salt, it is obvious that the reaction procedure of this application is equally as applicable to the ether alkali metal salts, particularly the potassium salt.

We claim:

1. The process of curing an isocyanate terminated urethane prepolymer which comprises curing an isocy- 10 anate terminated urethane prepolymer with at least one compound selected from those of the formula:

wherein R is a hydrocarbon, and R is selected from the group consisting of hydrogen, halogens, and hydrocarbons.

2. The process of curing urethane as claimed in claim 1 wherein said R is hydrogen.

3. The process of curing urethane as claimed in claim 2 wherein said R is alkyl.

4. The process of curing urethane as claimed in claim 3 wherein at least one cross-linking agent is bis(oaminophenylthio)methane.

5. The process of curing urethane as claimed in claim 3 wherein at least one cross-linking agent is bis(oaminophenylthio)ethane.

6. The process of curing urethane as claimed in claim 3 wherein at least one cross-linking agent is bis(oaminophenylthio 1 ,2 propane.

7. The process of making an elastomeric polyurethane plastic which comprises mixing an organic compound having reactive hydrogen atoms as determined by the Zerewitinoff method having a molecular weight of at least about 500, an organic polyisoyanate thereby forming a prepolymer, and curing said prepolymer by mixing therein at least one curing agent of the formula:

NH NH S-R-S wherein R is a hydrocarbon.

8. The process as claimed in claim 7 wherein said R 

1. THE PROCESS OF CURING AN ISOCYANATE TERMINATED URETHANE PREPOLYMER WHICH COMPRISES CURING AN ISOCYANATE TERMINATED URETHANE PREPOLYMER WITH AT LEAST ONE COMPOUND SELECTED FROM THOSE OF THE FORMULA:
 2. The process of curing urethane as claimed in claim 1 wherein said R'' is hydrogen.
 3. The process of curing urethane as claimed in claim 2 wherein said R is alkyl.
 4. The process of curing urethane as claimed in claim 3 wherein at least one cross-linking agent is bis(o-aminophenylthio)methane.
 5. The process of curing urethane as claimed in claim 3 wherein at least one cross-linking agent is bis(o-aminophenylthio)ethane.
 6. The process of curing urethane as claimed in claim 3 wherein at least one cross-linking agent is bis(o-aminophenylthio)-1,2 propane.
 7. The process of making an elastomeric polyurethane plastic which comprises mixing an organic compound having reactive hydrogen atoms as determined by the Zerewitinoff method having a molecular weight of at least about 500, an organic polyisoyanate thereby forming a prepolymer, and curing said prepolymer by mixing therein at least one curing agent of the formula:
 8. The process as claimed in claim 7 wherein said R is aryl.
 9. The process as claimed in claim 7 wherein said R is alkyl.
 10. The process as claimed in claim 7 wherein at least one cross-linking agent is bis(o-aminophenylthio)ethane.
 11. The process as claimed in claim 7 wherein at least one cross-linking agent is bis(o-aminophenylthio)ethane.
 12. The process as claimed in claim 7 wherein at least one cross-linking agent is bis(o-aminophenylthio)-1,2 propane. 